Ignition system



s. Gf; EsKlN 2,363,509

IGNITION SYSTEM Nov. 28, 1944.

Filed Oct. l-8, 1940 INVENTOR ATTO/wey.

`Patented Nov. 28., 1944 IGNITION SYSTEM Samuel G. Eskin, Pittsburgh, Pa., assignor to Robertshaw Thermostat Company, Youngwood, Pa., a corporation of Pennsylvania Application October 18, 1940, Serial No. 361,739

13 Claims. (Cl. 175-115) This invention relates to ignition systems and more particularly to electrical ignition devices for gaseous fuel burners.

Ignition devices of this type include those using an 'electrically heated coil of wire which is incorporated in a circuit embodying a relay device.

The relay introduces a time delay between the energizing of the ignition coil and the opening of the gas valve in order that the coil may reach igniting temperature before the gas begins to flow. The danger involved in permitting the escape of unburned gas is of common knowledge and itis essential that all contingencies which may subject these devices to this hazard be guarded against.

It thus becomes necessary in approaching this problem to consider not only the customary mode Lof operation of gaseous fuel burners, but also unusual acts which may prove hazardous if the ignition system is not, safeguarded in all conceivable ways. The principal defect in prior devices of this nature has been that the escape of unburned gas could occur under certain modes of operation of the ignition system. For example, where thermal elements have 'been utilized in the time delay relay device,there has often been insufficient time between turning the ignition on, then off, then on againfor this element to regain its original position and prevent the gas valve from opening before the ignition coil reaches ignition temperature upon the final operation.

Another problem to be considered in devices of this character. is that the ignition system is invariably subjected to the ambient temperatures of the fuel burner. Time delay relay devices are often of a type which change their timing if exposed to variations in ambient temperature.

AHence, unless compensation, 4with its attendant l and dependable operation of an electric ignition system for gaseous fuel burners.

Another object of the invention is to prevent continued iiow of gas upon failure of the' electric circuit or power supply to the ignition system.

Another object of the invention is to reduce the heat added by the ignition coil to an oven or the like where the fuel burner may be located.

Another object of the invention is to permit theuse of expensive materials for the ignition coil without adding materially to the initial cost of this element or to the cost of replacement.

Another object of the invention is to operate l thesystem on a Voltage which will ensure satisfactory switching.

' Another obiectof the invention is to forestall opening of the'gas valve under any conditions until the ignition coil has reached ignition temperature. Another object-of the invention is to reduce the time delay between energization' of the ignition coil and vopening of the gas valve to the. minimum consistent with safety.

Another object of .the invention is'to render,

Another object of the invention is to construct the device of a simple, compact and rugged design which will render it inexpensive to manufacture and reliable in operation.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawing wherein is shown a diagrammatic View of an ignition system ,embodying this invention. t

Referring more particularly to the drawing, an oven compartment I0 of a gas range is shown as having the usual gas burner I2 supported therein. In this instance, the flow of gas to the burner I2 is under control of a thermostatic regulator I4 which is interposed between the gas inlet I6 and the burner I2. The regulator I4 also embodies a main gas cock (not shown) having a rotatable operating stem I8 carrying the dial 2l) and by means of which the inlet I6 may be opened and closed in the usual manner. The thermostatic control of the oven I0 is completed by the provision of the thermal element 22 supported in the oven and operatively connected to-the regulator I l., As such controls are well-known and form no part of the present invention, further description is deemed unnecessary.

A solenoid gas valve 24 of any lmown type is interposed in the 'gas inlet line preferably between the regulator I4 and the burner I2. Such valves may be arranged, as in this instance, to be opened by energization of the solenoid and closed by gravity as is well known. A wire 26 connects the solenoid 'gas valve 2l to one terminal of a main switch 28 shown as supported by the regulator I4 adjacent the gas cock stem I8. Operation of the main switch 28 may be 'effected by a cam 29 carried Aon the stem I8 and arranged to 'close the switch'when the gas cock is rotated cock, or separately operable if. desired. The

other terminal of the main switch 28 is connected cases, may be omitted from the assembly. The.a

transformer 32 in the embodiment described is designed for use where current of 115 or 220 volts is supplied to the power line.

able low voltage, such as for instance, 12 volts. The resistor 36 limits the current flow to the ignition coil 40 allowing the use of a relatively short coil. While the resistor 36 is shown as being a wire or ribbon type, it will be apparent that a lamp, or a combination lamp and coil, may be substituted.

The ignition coil 48 is located in proximate relation to the burner I2 which it is. designed to ignite. Preferably, only the ignition coil 40 and the burner' I2 of this assembly are housed -within the oven I of the gas range when used in such relation, or in the combustion chamber of other devices.

This invention is particularly directed to the provision of means for delaying the admission of gas to the burner until the ignition coil has had suilicient time to reach lgniting temperature. To this end, a control relay having a time delay period is incorporated in the ignition system.

i As shown more or less schematically in the drawl ing, this control relay may comprise broadly a mercury switch 44, movable between open and closed positions, and an electromagnetic actuator 46 therefor in shunt with the circuit of the solenoid gas valve. The mercury switch may have oneterminal connected by a wire 48 to the wire Hand the other terminal connected by a wire 58 to the wire 42. 'I'he electromagnetic actuator 46 has one terminal connected by a. wire 52 to the wire 26 and the other terminal of the actuator is connected by a wire 54 to the wire 34.

The mercury switch 44 may be pivotally sup- .,ported at 58 ori a bracket 58 secured to a, panel '68. The pivotalsupport 56 extends throughthe bracket and) further serves as a pivotal connection for th armature 52. of the electromagnetic actuator 46. The mercury switch may thus beA tilted from one position to another to open and close the circuit. 'I'he mercury is adapted to flow freely when the switch is tiltedto close the circuit instantaneously, but is rrestricted in owing to open lthe circuit for a predetermined period of time. Inthe embodiment shown the switch is The transformer permits operation of the system at a suitwire 34, and wire 54. 'Ihe circuit back to the main switch 28 is completed by the wire 52 and wire 26 as described. Immediately upon energization of the actuator 46, the mercuryswitch 44 is tilted into the restricted now position but the switch remains closed until the desired time delay period expires. Coincident with the energization of the actuator 46, the current also flows through resistor 35, and the ignition coil 40.

Due to the mercury' switch 44 being connected in shunt with the solenoid gas valve 24 by wires 48 and 50, the solenoid coil is shorted out and the gas valve remains closed as long as the mercury switch is closed. rIfhe shunt, however, permits the circuit through the ignition cnil to be completed through'wire 26 to the main switch 28. Hence, while the mercury switch remains closed and the solenoid gas valve is also closed, the ignition coil is energized to-reach igniting temperature. expires, the circuit-'through the mercury switch opens and the current `flows through the solenoid gas valve 24 to open it and permit gas to flow to the burner l2. The ignition coil having at this time reached igniting temperature, the gas flowing from thewburner I2 is readily ignited for any predetermined period of time. Satisfac i tory results have been obtained with a delay period of fifteenv or twenty seconds during which the ignition coil reaches igniting temperature.l 'Ihe important feature of the deviceis that there' is an immediate resetting of the switch to closed position and a subsequent time delay period- .whenever the current is switched off or other wise discontinued through the energizing circuit of thignition' coil. Hence, what'may be termed an immediately Vrecycling ignition system is-propossible to create a flow of gas to the burner unless the ignition coil is at igniting temperature.

normally closed,.but it will be apparent that the closed position could be intermediate two open positions if desired. Devices of this character are well known in the artand many modifications could be made in the structure which has been described for illustrative purposes only. It will further be apparent that the invention is not limited to the use of a control relay embodying a mercury switch as othertypes. of relay vfulfilling the objects of the invention could beused as explained hereinafter.

In .the operation of the ignition system described, the closing of thepmam switch :s estab- It will be apparent that when the dial 2l is rotated to open the gas cock, thus closing the switch,28, the solenoid gas valve 24'wil1remain closed until lthe time delay period has expired.

It is only after this predetermined interval has ignition coil could reach sufficient temperature' ,to ignite it. Itwillbe remembered thatthe mrcury switch is immediately recycling and thus fullls a useful function. Should the dial 2l be rotated from the open position described to closed position, the main switch 28 will then be opened again. However, the mercury switch is automatically tilted t0 its initial position and immediately -closedduetoitsinstantresponseinthlsposition. The ignition .coil then begins to cool due to deenergization of itsfcircuit. Nowv should the time delay period must necessarily occur before lishes a circuit to one side of the electromagnetic the solenoidgas valve is energized to permit gas Thus, regardless of the As soon as the time delay period recycling feature of the control relay will always ensure the predetermined delay period whenever the main switch is opened.

yA further safety feature of the device is the constantly energizedI ignition coil. Should the gas be turned off at any point beyond the lmain gas cock, there is no interference with the electrical circuit to the ignition coil. Thus, as the ignition coil remains atigniting temperature it is always ready to ignite the gas as soon as it is again turned on.

It is apparent, moreover, that failure of the electrical circuit at any point in the system will result in immediate deenergization of the solenoid gas valve and its closure by gravity. No

- gasl can iiow to the burner while the circuit of the ignition coil `remains deenergized for when the shunt ceases to function.

The resistor 36 serves a useful purpose in make ing the operation of the ignition coil possible on any suitable voltage, such-as six or twelve Volts. The ignition coil can thus be made of a short piece of wire which also serves a useful purpose in permitting more efficient, but more expensive, materials to be used for this element. Moreover, the heat added to the oven compartment is reduced to a minimum by reducing the size of' the ignition coil and locating the resistor outside. As modern gas ovens are designed to operate under low temperatures, the elimination of undue added heat an important advantage.

-The preferred form of control relay has been described as embodying a mercury switch. Such devices are unaffected by ambient temperatures which may be as high as 300 degrees F. at the point of mounting on the range. Due to this feature there is no change in the timing of the relay which otherwise would require` compensatio-n. It will be understood, however, that the invention is not limite-d tothe preferred form lcle-- scribed, but that other suitable component parts may be substituted if desired..`

'I'he Various modifications which can be made in the details of construction and arrangement of partsV will be apparent to those skilled in the art, and can be made without departing from the spirit of the invention. In particular, an/y suitabletype of control relay having the time relayed operation and recycling features can be employed. Any type of resistor, including a signal lamp, can be substituted for the resistor described.

Also, any suitable type of burner requiring ignition can be used in conjunction with this system as well as the gas range type shown. Reference is, therefore', to beohad to the appended claims as defining the scope of this invention.

reclaim: 1 1. An electric ignitiondevice for fuel buners `comprisingin combination, an electrically operated valve for controlling the-flow of fuel to .said

, burner, an electric igniterCad-jacent the burner 4fuel valve, an electric oignition coil in the energizing circuit of said solenoid fuel valve, anda control relay comprising a switch for shunting said valve, said relay being adapted to delay opening said valve until the coil rea/.ches igniting temtrol relay for shunting said valve, said relay com-Y prising. a switch having time-delayed movement to open position and immediate movement to closed position, saidtime delayed movement permitting the coil to reach igniting temperature before the fuel valve opens, and means for actuating said switch to either of said positions.

4. An electric ignition device for gaseous fuel burners comprising in combination, a solenoid fuel valve, an electric ignition coil in the energizing circuit of said solenoid fuel valve, and-a control frelay for shunting said valve, said relay comprising'a mercury switch occupying a closed position when said circuit is deenergized. said switch having time-delayed movement to open position permitting the coil to reach igniting temperature before the fuel valve opens.

5. An electric ignition device for gaseous fuel burners comprising 'in combination, a solenoid fuel valve, an electric ignition coil in the energizing circuit of said solenoid fuel valve, and a 6. An electric ignition device for gaseousfuel burners comprisingin combination, a solenoid fuel valve, an electric ignition coil in the energizing circuit of said solenoid fuel valve, and a con-v ftrol relay for shunting said valve, said relay comprising a mercury switch occupying a closed position when said circuit is deenerg'ized, said switch having time-delayed movement to open position and being immediately reset for such movement 'in the closed position, said time-delayed movement permitting the coil to reachigniting tem' perature before the fuel valve opens, and electromagnetic means for 'actuating said switch to either of said positions.

7. An electric ignition device for gaseous fuel burners comprising inv combination, a valve for controlling the flow of fuel to said burner, electromagnetic meansofor operating said valve bey tween closed and open positions, an electric in-l candescent igniter adjacent the burner adapted to reach a temperature sufficient for igniting said fuel, a resistor for limiting current flow to said igniter, switching means for/connecting said ig niter and valve operating means' to a source of energizing current, and an electromagnetic relay energized during energization. of said igniter and operable for maintaining said valve closed during a. predetermined period following energize.-

- tion thereof and adapted to be immediately reset for such delayv period upon deenergization thereof, .said delay period being xed solely by said time-delay means and permitting said igniter to reach ignitingl temperature.-

8. An electric ignition device for gaseous fuel burners comprising incombtnation, a solenoidI fuel valve, an electric ignition coil inthe energizing circuit oiV said solenoid fuel valve, and a control relay for shunting said valve, said relay comprising a mercury switch occupying a closed position when said circuit is deenergized, said switch being tiltable upon energization of said 'circuit to cause opening thereof with time decuit of said igniter, switching means for connecting said igniter'and valve solenoid to a source of circuit is deenergized, i and an electromagnet having an armature connected to-said switch for eifecting said Vtiltable movement.

11. An' electric ignition device forgaseous fuel burners comprising in combination, electrically operated means for controlling the flow of fuel to said burner, electric igniting means for said burner in series circuit with said controlling means, means for energizing said igniting and controlling means, andl a control relay having a timing element connected in parallel circuit with said'controlling means and operable to delay energization of said controlling means until the igenergizing current, and an electromagnetic relay energized in response to energization of said igniter and operable for maintaining said valve closed irrespectiveof the temperature of said igniter for a period suicient for said igniter to reach 'igniting temperature 'andbeing adapted tp be immediately-reset for such period upon deenergization thereof.

`10. An electric ignition device for gas ranges comprising in combination, a gas burnerin the oven compartment of said range, a solenoid gas valve for controlling the iiow of gas to saidburner, an electric ignition coil in the energizing circuit of said gas valve and located in proximate relation with said burner, a resistor located outside said oven compartment and adapted to limit the current iiow to said igniter, andz a control relay for'shunting said gas valve, said relay comprising a mercury )switch occupying a closed position when said circuit is deenergized, said switch' being tiltable upon energization of said circuit to cause opening thereof with time delayed .action suiiicient to permit the coil to reach igniting. temperature before the gas valve opens and being immediately reset for such movement when said nitingmeans reaches igniting temperature.

12. An electric ignition device for gaseous fuel burners comprising in combination, electrically operated means for controlling the flow of fuel to said burner, electric igniting means for said burner in series circuit with said controlling means, means for energizing said igniting and controlling means, and a control relay for delayy ing energization of said controlling means until the igniting means reaches igniting temperature,-

said relay comprising a coil connected in parallel with said controlling and igniting means and adapted to operate a time delay switch connected in parallel with said controlling means only.

13. An electric ignition device for fuel burners having means for supplyingfuel thereto comprising an electric igniter, electrically operable means energizable for actuation to a position for Y admitting fuel to the burner, a main switch operable for causing energization of a circuit including said igniter and fuel admitting means,

and a control relay electricallyconnected to said fuel admittingmeansforl causing said means to tion of said circuit.

remain unactuated for a predetermined period following energization of said circuit, said relay including an initially closed switch which opens after a time delay period following energizatlon of said circuit and resets for such delay period substantially instantaneously upon deenergiza- SAMUEL G. ESKIN. l 

